Pulsed laser deposition of HfO2 thin films on indium zinc oxide: Band offsets measurements

One of the most used dielectric films for amorphous indium zinc oxide (IZO) based thin films transistor is HfO2. The estimation of the valence band discontinuity (ΔEV) of HfO2/IZO heterostructure grown using the pulsed laser deposition technique, with In/(In + Zn) = 0.79, was obtained from X-ray photoelectron spectroscopy (XPS) measurements. The binding energies of Hf 4d5, Zn 2p3 and In 3d5 core levels and valence band maxima were measured for thick pure films and for a very thin HfO2 film deposited on a thick IZO film. A value of ΔEV = 1.75 ± 0.05 eV was estimated for the heterostructure. Taking into account the measured HfO2 and IZO optical bandgap values of 5.50 eV and 3.10 eV, respectively, a conduction band offset ΔEC = 0.65 ± 0.05 eV in HfO2/IZO heterostructure was then obtained.